Sifeng and a 15-year-old companion, Jiaqian Liu, disappeared from Lyndhurst, New Jersey on February 1, 2011. The girls are both Chinese nationals and had traveled to the United States with a tour group. They were last seen at the Quality Inn on Polito Avenue at 1:20 a.m. They were reported missing an hour later. They had unpacked their suitcases and put their clothes in backpacks which disappeared with them, but left their passports. One of the girls called her parents in China shortly after she vanished and said she was safe.

A photograph of Jiaqian is posted below this case summary. She was found safe in August 2012, but Sifeng remains missing. Authorities believe she left of her own accord and may be in New York. Her case remains unsolved.